Machine-switching telephone system



A. E. LUNDELL.

MACHINE SWITCHING TELEPHONE SYSTEM.

APPLICATION FILED MAR. 25, I9I8.

A. E. LUNDELL.

MACHINE swlTcHlNG TELEPHONE SYSTEM.

APPLICATION FILED MAR 25, T918 con 00 QN m M JU E b I 5d b IM H M d MH o n@ o o owv l H M m m WNN o o\m.%m. NNN. u e 1a H 0 o d r 1 V E m ,Pd EN@ M n f e m l mmm D.. will. J||} M QQ Q l n L ,l im a o msm mmm A. E. LUNDELL. n MACHINE SWITCHING TELEPHONE SYSTEM.

APPLICATION FILED MAR. 25, 191s.

1,341,473. Patented May 25,1920.

4 SHEETS-SHEET 3.

A. E. LUNDELL. MACHINE SWITCHING TELEPHONE SYSTEM.'

APPLICATION FILED MAR. 25, I9I8.

1,341,473., l Patented May 25 1920.

4 SHEETS-SHEET 4.

Ulll'l'iE 'S'lATES FATE? FFlE.

ALBEN E. Lunnnnr., or NEW Yoan, n. Assrenon. fro wns'rnan ELEoTnIc COMPANY,

INCORPORATED, OF NEW' YRK, N. Y., UORGRATON OF NEW YORK.

MACHINE-SWTCI-IING TELEPHDNE SYSTEM.

Latinas..

Application led 'March 25, 1918.

To @ZZ whom t may concern Be it known that I, ALBEN E. LUNDELL, a citizen ot the Unite@ States, residing at New York, in the county of Bronx, Stateof New York, have invented certain new and useful improvements in hlachine-Switching Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to machine switching telephone systems of the type wherein a repeating relay at the central oiiice is operated by a sender to t `ansmit impulses to the stepping magnets to set the switches.

The object of the invention is similar to that disclosed in latent No. 1,252,978, granted to Williams and Sperry on January S, 1918. The invention consists oi improvements in the circuits whereby the system may be made to work more reliably and with less apparatus.

A feature of the invention is the means whereby the results obtained in the said patent may be accomplished without the use of certain time and current marginal relays.

Other new and useful lfeatures will be set forth in the following description and drawings, in which Figure l is a diagrammatic representation of a calling telephone station and a line finder switch, Fig. 2 is a diagrammatic representation ot' a selector switch; Fig. 3 is a diagrammatic representation oft a connector switch; and Fig. et is a (iliagrammatie representation ot the circuits and apparatus comprising` a trunk to a central oiiice, including certain apparatus at such central office. Figs. l, 2 and 3, taken together', illustrate a connection between two subscribers in one central oilice; and Figsl, 2 and 4 taken together illustrate a connection between a subscriber in one central ofhce and an operator in another central oiiice.

Brief" description of tite operation.

A calling subscriber may establish a connection either with a subscriber within the same exchange, in which case such connection is shown diagrammatically by Figs. l, 2 and 3. or to an operator at a distant point, in which case Figs. l, 2 and er are to be used.

llihen the calling subscriber upon removing` his receiver causes the line finder, shown in Fig. l, to be actuated, as will be more Specification of Letters Patent.

Patented May 25, 1920.

Serial No. 224,496.

fully described hereinafter, the side switch of the line finder moves successively through positions l and 2 to position 3, at which point the first selector associated therewith, shown diagrammatically in Fig. 2, is caused to be directively actuated. Here in turn the first selector side switch moves successively through positions l and 2 to position 3. Thereafter either the apparatus of the connector switch, shown in Fig. 3, will be actuated, or the apparatus connected with the trunk to the distant point, shown in Fig. l, will be actuated.

lt the connection is directed to a local point, a circuit will be set up including the escape magnets of the first selector and the connector in series (Fig. The escape magnet of the connector will be energized and denergized to perform its proper functions by a shunt circuit through the use ot which the escape magnet oiI the first selector' will be maintained energized until the last series of impulses has been sent. Thereupon, the action of the connector side-switch magnet will break this circuit and the iirst selector side switch will move to its fourth position. .lt will be noted then that during the conversation over a local connection, the side switch ot the finder in the third position and the side switch of the rst selector is in the fourth position, and the battery feed is local. Through this arrangement the action of the first selector side switch is made positive, not depending on a time marginal impulse as in the lVilliams and Sperry patent hereinbe'lore mentioned.

lf, however, the connection is directed to a more distant point, the selection of a trunk leading thereto will automatically7 operate to cause the iinder side-switch magnet, instead oi the selector sideswitch magnet, to be included in an extended circuit, and to become and remain energized until the connect-ion is fully established. In this case it the connection is established over a trunk to a manual operator (Fig. el), the finder side-switch magnet becomes energized upon 'the seizure oi such a trunk and so remains until the operator, in answer to the summons ot the line signal, inserts a plug into the calling trunk. rfhereupon the action of a single relay, responding to the insertion of the plug, opens this energizing circuit, and the finder side-switch magnet becoming denergized causes the movement et the wipers into the fourth position. Through this arrangement the action ot' the finder side switch is made positive, and not dependent on a current marginal impulse as in the Villiams and Sperry patent hereinbetore mentioned. lt will be noted that during the establishment of a connection toV a distant point, therefore, that the side switch of the nder is in the fourth position and the side switch of the first selector is in the third position, and thus the talking battery is supplied from the distant point.

Detailed description (beppe/infinit.

Upon the removal ot the receiver at sub station A, line relay 100 is energized and in attracting its left armature, it creates a calling condition upon the multiple terminals 101 in the iinders in which such line appears. ln attracting its right armature, it energizes relay 102 to start a line finder in search of the calling line. Relay 102, in attracting its upper armature, locks itself to conductor 103, independently of the right armature and back contact of relay 104, and in `attracting its lower armature applies ground to multiple segments 105, individual to the group oflines to which substation A belongs, and also closes the circuit ot the primary magnet PM with the line linder as follows: ground, lower armature and front contact oi' relay 102, conductors 106, 107, armature and back Contact ot relay 10S, conductor 109, side-switch arm 110 and its iirst contact, armature and back contact ot magnet PM, magnet PM, tree pole ot battery.` T his magnet makes and breaks its energizing circuit, thus rotating the finder brush shaft 153. The attraction of lower armature oi' relay 102 also closed a circuit tor relay 111,

in parallel with that traced Jior magnet PM: f

ground, lower armature and 'front contact of relay 102, conductors 100 and 107, armature and back Contact of relay 108, conductor 113, relay 111, free pole of battery. Relay 111 connects the brush 114 to the escape magnet ESC. At this time, however, the escape magnet does not operate since it is shunted over the path traced, including the armature and back contact ot magnet PM. Magnet PM energizes in the circuit traced and near the end ot its strolre, opens the shunt about the escape magnet, at which time the brush 114` is in contact with grounded group segment 105 and becomes energized over the following circuit: tree pole ot battery, magnet PM?, magnet ESC, conductor 115, left armature and front contacts of relay 111, brush 11%, segment 105 to ground, at the lower armature and trout Contact ot relay 102. rlhe escape magnet is constructed to release the side switch from position. 1 to position 2, upon its energizatiou.

In position 2 the escape magnet is euergized over the following circuit: Jfree pole of battery, magnet PM, magnet ESC', armature and back contact of relay 117, arm 118 and its second position contact, to ground. In position 2, arm 110 closes the 'following circuit from magnet SM, to step the positioned iinder brushes 120, 121 and over the multiples 123, 124- and 101 of the group to which substation A belongs: tree pole of battery, magnet SM, its armature and bac-k contact, armature and front contact ot magnet ESC, arm 110 and its second contact, conductor 107 to ground, at the lower armature and front contact of relay 102.

Then the test brush 122 travels over test contacts 101 of the selected group, a circuit is established for relay 117 from ground, winding of relay 117, brush 122, contact 101, winding oi cutoff relay 127, to tree pole of battery. The current flowing in this circuit, as it is successively made during the travel or' brush 122, is insuliicient to cause the energization of either of the relays 117 or 127.

VHowever, when the test brush 122 reaches the multiple 101 of substation A, the following circuit is closed to operate relay 117 and to stop the movement ot the line iinder: free pole of battery, resistance 125, left armature and front contact ot `relay 100, conductor 126, multiple 101, brush 122, relay 117 to ground. ln this circuit, relay 117 is energized, whereupon a circuit is momentarily established from ground, side-switch wiper 118 and its second contact, armature and front contact of relay 117, brush 122, terminal 101, to a point where the circuit divides, part of the current flowing through the winding of relay 127, tree pole ot battery, and the remainder iiowing over the group conductor 126, tree pole of battery, through the circuit heretofore described. rlhis current flowing through the relay 127 is sufficient to energize it, whereupon the line relay 100 becomes denergized and the calling condition on the multiple 101 removed. Y

Upon the attraction of its armature by relay 117, the circuit for the energization of magnet ESC is opened and in retracting its armatures, it causes the movement ot the side-switch wipers into their third position, and at the same time stops the further m-ove- 115 ment oit' the brushes 120 to 122. The current now flowing over the circuit through relays 117 and 12'( 1n series, is suilicient to cause the continued energization of relay 127 and by the changed potential on terminal 101 to 120 mark the calling line as busy.

As the side-switch wipers move into their `third position, and as the line relay 100 becomes denergized, relay 102 becomes de'e'nergized to remove ground from the starter conductor 107 and to restore the continuity of the in-started wires 129 and 107.

ln the third position of the nder side switch, the following circuit including the calling line is closed for the impulse relay 130 13.1, tree pole of battery, right winding of relay 131, conductor 132, arm 135 and its third position contact, brush 121,l contact 12-1, through the telephonie appa atus at substation A, terminal 123, brush 120, sideswitch arm 13G and its third position contact, conductor 13S, left winding ot relay 131, to ground. Relay 131, in operating, energizes a slow relay 139. Relay 139, in attractingl its right armature, interposes a break in the circuit ot the release magnet RM. ln attracting its lett armature, this relay causes the energization ot' relay 103 through a circuit extending from ground, le'it armature and liront contact of relay 139, right armature and back contact ot release magnet Rll, right-hand winding of relay 103 to ground. rit the same time a circuit for the transmission of impulses to the selector switch, is established .trom ground at the secondary oil-normal contacts ot thc iinder switch, the armature and back contact ot relay 131 (closed only during the transmission ot the impulses), the right armature and iront contact oi' relay 139, side-switch arm 142 and its third contact, slow release relay 201), side-switch arm 201 and its iirst Contact, side-switch arm 146 and its third contact, thence over the upper heavily drawn conductor 147, the side-switch arm 202 and its tirst contact winding of selector primary magnets PMQto free pole ot battery.

During the transmission of the first series ot impulses over this circuit in response to the actuation ot the dial at the substation A., relay 200 is continually energized and selector' primary magnet PM is intermittently energized to rotate the selector switch shai't 203, Vcarrying brushes 204, 205, 206, and 207. The energization ot relay 200 causes the energization ot the selector' switch escape magnet ESC', through a circuit eX- tending from ground, front contact and armature ot relay 200, side-switch Aarm 208 and its first contact, escape magnet ESC to free pole ot battery.

At the end ot' this series of impulses, brush 20a may be set on segment 209 individual to the group of lines terminating in connector switches leading to local subscribers. Also at the end of this series of impulses, the slow release relay 200 becomes denergized and causes the breaking of the circuit :tor the energization ot the selector escape magnet. The denergizationot this magnet effects the movement oit the sideswitch wipers into their second position, and thereupon a circuit is established for the energization ot the selector switch secondary magnet SM from ground at the side-switch arm 210 and its second contact, back contact and armature of secondary magnet SM, magnet SM, to free pole oit battery. Magnet SM breaks its own circuit and causes the movement ot brushes 205, 20G and 207 over the terminals ot' the selected group of lines.

As the selector side switch moves into its second position, a circuit is again established tor the energization of escape magnet ESC from ground, selector switch secondary ot'f-normal Contact SON, conductor 21e, side-switch arm 215 and its second contact, winding ot escape magnet ESC', to tree pole ot battery. As the selector' switch takes its first secondary step and the brush 207 `encounters the iirst trunk of the group andu the ground at the secondary ott-normal contact SON is removed, the circuit ot the escape magnet will be broken unless this lirst encountered trunk is busy. In such a case, ground is connected to the escape magnet ESC, through a circuit extending from ground, on the terminal 213, brush 20T, sideswitch arm 215 and its second contact, to the winding 01"' escape magnet ESC. The secondary movement ot the selector switch will continue unless an idle trunk is encountered, at which time the absence of ground on terminal 213 will allow the deenergization of escape magnet ESC and thereby cause the movement ot' the side-switch arms into their third positions. The movement of sideswitch arm 210 from its second to its third position stops the action of secondary inagnet SM and lea-yes the brushes 205 to 20T in Contact with terminals 211 to 213. The connection is now built up to the point where the connector switch in Fig. 3 is actuated, which results trom the next series of impulses :trom the subscribers station A.

As the terminals 211 to 213 are seized, a circuit is established from ground, the sideswitch arm 11S and its third contact, conductor 119, third position contact and sideswitch arm 215, brush 207, terminal 213, conductor 325, right armature and back contact ot release magnet R21li2,side-switch arm 317 and its tirst contact, winding of relay 300, tree pole of battery. Through this circuit relay 30() is energized and attracting its armatures establishes a circuit for the transmission ot the nextseries of impulses, which circuit may be traced over the impulse circuit as described, the conductor lili', thence to lbrush 205, terminal 211, conductor 301, conductor 302, outer right-hand armature and front contact of relay 300, sideswitch arm and its first contact, primary magnet P2M?, tree pole of battery. lt should be noted that when the brushes `205 to 207 are moved into association with terminals 211 to 213, a circuit is established from the iree pole of battery, escape magnet ESC', baclr contact and lett-hand armature of relay 216, third position contact oft sideswitch arm 208, third position contact ot side-switch arm 217 over conductor 213, brush 296, terminal 212, conductor 311, conductor 312, first position contact and sideswitch arm 313, armature and contact of ringing relay 314, winding of escape magnet 310, to ground. Escape magnet 310 is energized in this circuit, but due to the transmitting circuit just described, it is immediately shunted and caused to denergize through a ground being placed on the circuit between side-switch arm 208 and sideswitch arm 21T at the armature of the contact of relay 200. l1`he denergization of escape magnet 310 causes the side-switch arms to move `into their second position without disturbing the train of impulses being transmitted to primary magnet P2M? fit the termination of this first series of impulses, the ground at the armature and contact of relay 200 is removed through the denergization of relay 200, and magnet 310 is again energized over ously traced. Upon this second energization of the connector escape magnet, the connector side-switch arms are moved into their third position. However, the continuity of the circuit including' the escape magnets 310 and ESC of the selector is preserved, both being energized.

The units series of impulses is now transmitted and upon the energization of relay 200, escape magnet 310 is again shunted, but this time does not cause a movement of the side-switch arms. The impulses in this last series are transmitted over the circuit heretofore described as far as side-switch arm 303, thence through the third position contact to secondary magnet S21/I2 to free pole of battery. Through these impulses, the brushes of the connector switch 30-1 to 306 are placed on the terminals 307 to 309 of the called line. 1n the third position the continuity of the impulse circuit through contact and outer righthand armatureV of relay 300, is preserved through the continued energization of relay 300 in a locking circuit, extending from ground, finder side-switch arm 113 and its third Contact, conductor 119, selector side-switch arm 215 and its third contact, brush 20T, terminal 213, conductor 325, right-hand armature and back contact of connector release magnet RZMQ, connector side-switch arm 31T and its third contact, contact and inner right-hand armature of relay 300, winding of relay 300, to grounded battery.

lt will be remembered that relay 300 was energized through this circuit as far as sideswitch arm 317, thence through the first and second contacts thereof, directly to the winding of relay 300. As the side-switch arm 317 vmoved from second to the third contact, relay 300 did not become denergized, due to the fact that side-switch arm 317' bridged its second and third contacts as it passed from one to the other.

the circuit previl 1n the third position, as soon as slow release relay 331 is "energized through a circuit eXtending from the ground on conductor 325, as described, third position contact and side-switch arm 332, winding of relay 331, free pole of battery, a substitute circuit for relay 300 is provided. r1`his circuit extends from the right-hand inner armature and contact of relay 331, the right-hand inner contact and armature of relay 300, winding of relay 300, to free pole of battery.

At the cessation of the last series of impulses and the removal of the ground at the contact and armature of relay 200, the escape magnet 310 is again energized and the connector side-switch wipers are moved into their fourth position.

r1`hereupon the escape magnet ESC of the first selector switch will be denergized and the rst selector side-switch wipers moved into their fourth position. It is pointed out that this is a specific improvement over the arrangement shown in the lVilliams and Sperry patent before mentioned, where the movement of the first selector side switch depended on a momentary impulse being transmitted back to the side switch from an armature on the relay 331.

1f the called line is busy, a ground will be found on the terminal 309-, and this being connected through brush 306, the side-switch arm 316 to the left-hand high resistance winding of relay 315, shunts this relay and causes it to remain denergized; thereupon relay 331 becomes denergized and removes the ground, which energizes relay 300 through the inner right-hand armature of relay 331. Since side-switch arm 317 in its fourth position does not function in the energization of the relay 300, this last relay retracts its armature and establishes a circuit from ground, the secondary off-normal contact S2O2N2, the back contact and left-hand armature of relcy 300, the connector release magnet R2M2, to free pole of battery. The connector' release magnet upon energization releases the brushes 304 to 306 and causes them to return to their normal positions, at the same time the side-switch arms are returned to their normal positions, but release magnet RZB/l2 is held energized through a circuit extending from a ground on conductor 325, the right-hand armature and front contact of release magnet RZMZ, the resistance 322, Contact 320 of primary off-normal contact PZOZNZ, conductor 321,

Vthe contact and left-hand armature of relay 300 to the winding of release magnet RZMZ. Through the attraction of its left-hand armature, release magnet R2M2 applies the source of busy tone 326 to the first position contact of side-switch arm 327, thence through the condenser 323, conductor 330.

conductor 3,11, terminal 212, brush 206, con- 'ductor 21S, side-switch arm 217 and its fourth position Contact, left-hand winding of called super fisory relay 219, to free pole of battery. Through the 'inductive coupling of the right and left-hand windings of relay 219, the busy tone is transmitted to the calling subscribers instrument in a well-known manner. Then the calling subscriber recognizes the tone and in answer thereto, replaces his receiver on its hook, relay 131 becomes denero'ized, whereupon the finder release magnetltM is energized over a circuit from ground at the primary off-normal contact or secondary off-normal contact of the iinder, the armature and back contact of relay 131, the armature and back contact of relay 139, the armature and back contact of relay 111, winding of release magnet RM, whereby the finder is released. This ground is also extended from the armature and back contact of relay 111, over the conductor 125 to the selector release magnet RM and thence to free pole of battery, whereupon the selector is released. Upon moving brush 207 away from terminal 213, continuity of the locking circuit of connector release magnet RZM2 is broken and the connector switch is placed in its idle condition.

Should, on the other hand, the called line prove to be idle, a circuit is established from free pole of battery, through the winding of cutofll relay, similar to the relay 127, terminal 300, brush 306, side-switch arm 316 and its fourth contact, the left-hand high resistance winding of relay 315 to ground. Relay 315 is energized in this circuit, and through the attraction of its inner righthand armature, a circuit is established from ground, right-hand winding of relay 315, contact and inner right-hand armature of relay 315, fourth position contact and sideswitch arm 332, winding of relay 331, to free pole of battery. 1n the interval between the movement of the side-switch arm 332 from its third to its fourth position and the attraction of its armature by relay 315, relay 331 remains energized due to its slow releasing features. Through the attraction of its lefthand armature the high resistance winding of relay 315 is shunted and the potential of terminal 309 is so changed that this line in the other positions of the multiple, in which it appears, is marked as busy.

1t will be remembered that at the cessation of the last series of impulses, the relay 310 became energized in the same manner as at the cessation of the previous series of impulses and upon energization it movedI the side-switch arms into their fourth positions. As the arm 313 moves from the third to the fourth position, the continuity of the circuit through the connector side-switch magnet 310 and the selector side switch ESC was broken 5 thereupon the selector side-switch magnet became deenergized and moved its arms into their fourth positions. The connector side-switch magnet, however, does not become denergized since it finds a new circuit extending from free pole of battery, resistance 340, contact and outer righthand armature of relay 331, fourth position contact of side-switch arm 313, and thence over the circuit previously traced, including the winding of escape magnet 310.

In this fourth position, ringing current is applied from the source of ringing current 334, winding of ringing cutoff relay 314, middle right-hand armature and contact of relay 315, fourth position contact 0f sideswitch arm 335, brush 305, contact 308, thence through the call bell 330 of the called subscriber, substation terminal 307, brush 304, side-switch arm 337, and its fourth position contact, contact and outer righthand armature of relay 315, to ground. When in response to the summons of a call bell, such called subscriber removes his receiver from its hook, the current in this circuit is so increased that relay 314 attracts its armature, thereby breaking the continuity of the energizing circuit of the side-switch magnet 310. The side-switch arms are moved into their fifth positions, and the talking circuit is thereby established. This may be traced from the calling subscriber at substation A., terminal 123, brush 120, sideswitch arm 130 in its third position, conductor 137, condenser 220, side-switch arm 221 and its fourth position contact, and sideswitch arm 201 and its fourth position contact, third position contact and side-switch arm 146, conductor 147, brush 205, terminal 211, conductor 301, fourth position contact and side-switch arm 337, brush 304, terminal 307 to and through the telephonie apparatus of the called subscribers substation, terminal 308, brush 305, side-switch arm and its fourth position contact, conductor 311, terminal 212, brush 206, conductor 21S, sideswitch arm 217 and its fourth position contact, fourth position contact and side-switch arm 222, condenser 223, third position contact and switch arm 135, brush 121, terminal 124, to the telephonie apparatus of the called subscribers substation A. Battery for talking purposes is fed to the calling subscribers substation through the windings of relay 1,31, and battery for talking purposes is fed to the called subseribers substation through the winding of relay 219.

Upon the termination of the conversation, the calling subscriber in replacing the receiver on its hook, causes the release of the connector switch', in the manner heretofore described.

The operation of setting up a connection to a distant point as illustrated in the use of Figs. 1, 2 and 4, proceeds in the manner described, up to the point where the selector switch of Fig. 2 has been direetively set on a certain group of lines. Those lines which lead to distant points with equipment such as is shown in F ig. 4 are provided with a conductor 224, leading to a commutator seg ment 225, associated with a brush 204. At

Vloclrs up over a circuit including ground from both .tliepriinary off-normal contact PON and the secondary off-normal contact SN, the second position contact of side-switch `arm 227, conductor 228, contact and right-hand armature of relay 216, winding of relay 216, to free pole of battery.

11n idle trunk in this group is selected in the same manner as heretofore described and the sideswitch arms are moved into their third positions; thereupon ground is connected from side-switch arm 118 and its third position contact, conductor 119, third position contact and side-switch arm 215, brush 207, terminal 213, conductor 400, winding of relay 401, to free pole of battery. Relay 401 attracts its armature and thereby establishes a circuit for the energization of line relay 402, which extends from free pole of battery, right-hand winding of relay 402, inner armature and contact of cutoff relay 403, `conductor 404, to a point where the circuit divides, partof the current flowing through the .right-hand winding of relay 405 and part flowing through the resistance 406, thence through the left-hand winding of relay 405, Contact and armature of relay 401, outer contact andv right-hand armature of relay 407, conductor 408, Contact and outer armature 'of cutoff relay 403, left-hand winding of line relay 402, to ground. Relay 405 does not energize in this circuit due to the high resistance of the windings of 402. The energization of line relay 402 causes the actuation of signal 409. Upon the seizure of this trunk, a circuit is established from ground, the left-hand armature and outer contact of relay 405, conductor 412, conductor 413, terminal 212, brush 206, conductor 218, sidesswitch arm 217 and its third position contact, side switch arm 208 and its third position contact, left-hand armature and front contact of relay 216, conductor 229, third position contact and side-switch arin 126, winding ofescape magnet ESC, winding of primary magnet PM, to free pole of battery. n

The finder escape magnet is energized through this circuit, but does not cause the movement of the finder side-switch arms to their fourth positions until the ground at the left-hand armature and back contact of relay 405 is removed.

I1`he operator, observing the illumination of signal lamp 409, inserts a plug 410 into jack 411. It will be observed that the current flowing through the windings of relay 405 up to this point is supplied through the windings of the line relay 402. Due to the resistance of these windings, current for this circuit is insufficient to cause the ener- `gization of relay 405. However, as the plug 410 is inserted into the jaclr 411 and the cuto relay 403 is energized in a wellknown manner, current is supplied to the windings of relay 405 through the windings of the repeating coils 414 and 415. This current is great enough to cause the energization of relay 405, which by attracting its armatures, removes the ground from the finder switch escape magnet and causes the movement of the finder side-switch arms into their fourth positions and at the same time causes the energization of relay 407 to extend `the talking conductors to the windings of the repeating coils through jack 411 and the plug 410. The energizetion of relay 405 also causes the conductor 400 to be grounded through the left-hand armature and front contact of relay 405. rThis ground replaces the ground on conductor 119 from the side-switch arm 11S,

- since this side-switch arm is now moved into the fourth position.

The conversational circuit is now .i'iully completed and may be traced from the winding 414 of the repeating coil through the tip of the plug 410, the tip of the jack 411, conductor 406, the right-hand armature and inner contact of relay 407, the conductor 416, terminal 211, brush 205, conductor 147, side-switch arm 136 and itsfourth position contact, brush 120, terminal 123 to and through the telephonie apparatus at substation A, terminal 124, brush 121, sideswitch arm 135and its fourth position con tact, conductor 150, conductor 21S, brush 206, terminal 212, conductor 413, left-hand armature and Contact of relay 407, to a point Where the circuit divides, part of the current going through the right-hand winding of relay 405, and part going through the resistance 406, thence through the conductor 404, the ring of the jack 411, the ring of the plug 410, the supervisory relay 417, the winding of the repeating coil 415, to free pole of battery.

1t will be noted that current for talking purposes is fed to theA calling substationA from the battery at the repeating coil 414-415. y

During the conversation and after the lnder side switch has moved into its fourth position, the release magnet of the finder is prevented from becoming energized through the ground placed on conductor 119 in the manner described, which is extended through the fourth position contact and side-switch arm 110, to the conductor 113, and thence to relay 111. Hence, the ground trom the primary and secondary ott-normal cont-acts through the righthand armature and back contact ot relays 131 and 139, is prevented from reaching the winding ot release magnet RM. However,

-when the calling subscriber replaces his receiver on its hook, the supervisory relay A11.17 is caused to denergize and the super visory lamp i18 is caused to light up in a well-known manner.

The operator thereupon removes the plug L110 from the jack 411, the relay 405 becomes de'elnergized and ground is removed from the conductor 400 by the retraction of the left-hand armature of relay 4105, so that the relay 111 becomes denergized; thereupon the circuit for the energization ot the finder release magnet is completed and the built-up connection is restored in the manner previously described.

lVhat is claimed is:

1. 1n a telephone system, telephone lines, trunk lines, selective switches for intercon necting said lines and for connecting said telephone lines and said trunk lines, mea-ns included in said switches for automatically differentiating between connections estab lished from a telephone line to a telephone line and from a telephone line to a trunk line, an arrangement controlled by said means for supplying talking 'current in the one case from battery-'feed coils located at said selector switches and for excluding said battery-feed coils in the other case, positive means for causing said arrangement to be actuated when a connection is established between telephone lines, and a single relay for causing said arrangement to be actuated when a connection is established between a telephone line and a trunk line.

2. ln a telephone exchange system, the combination with telephone lines, means tor propagating and transmitting series of impulses, selective switches responsive to said impulses for interconnecting said lines, means in certain of said switches for autoinatically differentiating between connections established between local points and more distant points, connecting circuits leaf'ling from said certainswitches to dis tant points, a switching arrangement responsive to said means for controlling the supply of talking current arranged to be actuated step by step, said arrangement being initially responsive to successive stages iii the operation ot the said certain switches and responsive for its final actuation to the complete establishment of the connection, positive means being included in the last et said switches used in a local connection for actuating said arrai'igement, and a single relay being included in the connecting circuit to the more distant point for actuating said arrangement.

1n a telephone exchange system, the combination with an automatic otlice, a manual oiice, telephone lines terminating therein, a connecting circuit including an impulse relay, condensers, and a selector in said automatic o'llcice, trunlrs terminating therein leading to said manual oiiice, means including said impulse relay and selector Jfor setting up a connection in said automatic oiiice or causing said selector to pick ont one of said trunks leading to the manual cnice, a. side switch adapted in one position to feed current to the calling line through the windings of said impulse relay and in another to cut ott" said coil and condensers and extend the calling line directly to the selector brushes, a circuit for advancing said side switch to cut oil said condensers, a relay adapted to be operated to prepare said circuit when said trunk is selected, and means comprising a single relay controlled by the operator at the manual office for closing said circuit and means for feeding current to the calling line over the seized trunk.

l. In a telephone system, telephone lines, connecting circuits and automatic switches for interconnecting said lines, condensers in said connecting circuits for conductively separating the two ends thereof, a side switch normally disconnecting said condensers from the called end of said connecting circuit, a side switch associated with the last of the train oit automatic switches, an escape magnet for each of said side switches, a circuit extending in series through the escape magnets of each of said side switches whereby the first mentioned side switch is controlled to connect said condensers in circuit with the called line when said circuit is broken, and means for b reaking said circuit.

5. In a telephone exchange system, the combination with telephone lines, senders therefor, a connecting circuit including automatic switches, a repeating` relay in said circuit operated by said senders to set said switches, and condensers in said connecting circuit between said relay and switches, ot a side switch normally disconnecting said condensers from the called end ot said connecting circuit, an escape magnet for said side switch, a circuit for the escape magnet of said side switch whereby the side switch is advanced to connect said condensers in circuit with the called line, said circuit extending into the circuit ot the last of the train of automatic switches, and means therein for controlling said escape magnet circuit incident to the setting of said last of the train of automatic switches on the terminals of the called line.

6. In a telephone exchange system, the combination with telephone lines, senders therefor, a connecting circuit including automatic switches, a repeatingrelay in said cir-` cuit operated by said senders to set said switches, and condensers in said connecting circuit between said relay and switches, of a side switch normally disconnecting said condensers `from the called end of said connecting circuit, and means for advancing said side switch to connect said condensers in circuit with the called line as soon as the last series of impulses has been transmitted.

'7. In a telephone exchange system, the combination with telephone lines, senders therefor, a connecting circuit including auto# matic switches, and a repeating relay in said circuit operated by said senders to set said switches, of condensers in said connecting circuit between said relay and switches normally disconnected from the called end of the connecting circuit, and means for con necting rsaid condensers in circuit with the called line as soon as the last series of impulses has been transmitted. l

8. In a telephone exchange system, the combination with telephone lines, link circuits, means for interconnecting a calling and a called line over a number of said link ircuits in series, a source of talking battery at an intermediate one of said link circuits, a side switch, a magnet adapted to advance the same to connect said source to said link circuit upon its denergization, means for energizing said magnet, means for maintaining said magnet energized including a circuit at each succeeding link circuit, and means fior denergizing said Ymagnet when the connector is set on the called line.

9. In a telephone exchange system, the combination with telephone lines, switches adapted to interconnect the same, a source of talking battery at an intermediate one of said switches, and an electromagnetic responsive device at said switch adapted to connect said source to said switch, means for including said device in a circuit extended to each succeeding switch in series, and means for altering the condition of said circuit when connection is made with the called line to operate said 'device to connect said source thereto.

l0. In a telephone exchange system, the combination with telephone lines, link circuits, an automatic selective switch for interconnecting a calling and a called line over a number of said link circuits in series, a source of talking battery at an intermediate one ot said link circuits, an electromagnetic responsive device at said switch adapted to connect said source to said link circuit, a circuit including said device and the link circuits in series, and means automatically actuated when connection is made with the called line for rendering said circuit eiiective to operate said device.

ll. In a telephone exchange system, the combination with telephone lines, automatic switches including selectors and a connector, stepping magnets therefor, a sender adapted to operate said magnets to set such switches to interconnect said lines, a source of talking battery at one of said selectors, a side switch for said selector, means for advancing said side switch when said selector is set to place said sender in operative relation to the magnets of the succeeding switches, means for maintaining said side switch in said position while `said succeeding switches are being set, and means for advancing said side switch to connect said source ot talking battery to the selected line when the connector is set thereon.

l2. In a telephone' exchange system, the combination with telephone lines, a link circuit, trunks leading `to local connections, trunks leading to more distant points, means for interconnecting a calling and a called line over said link circuit and a number of said trunks of either kind, a source of talking battery at said link circuit, two side switches, a magnet for each arranged to advance the same upon its denergization, means for energizing one oic said magnets automatically Vdetermined in accordance with the trunk selected, means for maintaining said energized magnet energized in cluding a circuit at each succeeding trunk, means for denergizing said energized magi net when the connection is fully established,

and means including said side switches for connecting said source of talking battery to said link circuit if the trunk selected leads to a local connection and for excluding said source of talking battery from said link circuit if the trunk selected leads to a more distant point.

In witness whereof I hereunto subscribe my name this 19th day of March, A. D. 1918.

ALBEN E. LUNDELL. 

